Stepping motor feed for a grinder including a high speed slewing motor



March 5 LOCKWOOD ET AL STEPPING MOTOR FEED FOR A GRINDER INCLUDING '7Sheets-Shet l A HIGH SPEED SLEWING MOTOR Original Filed Oct. 16. 1963GEORGE H.LOCK WOOD GLENN D. JOHNSON EDWARD G. ROBILLARD HENRY E.. H/RVIFIG. I

INVENTORS.

March 5, 1968 G. H. LOCKWOOD ET AL 3,372,322

STEPPING MOTOR FEED FOR A GRINDER INCLUDING A HIGH SPEED SLEWING MOTOROriginal Filed Oct. 16, 1965 7 Sheets-Sheet 2 MRNUAL FLU) FEED mm (mWNEELHEA D START GEORGE H. LOCK WOOD FIG 2 GLENN D. JOHNSON EDWARD G.ROBILLARD v HENRY E. HIRV/ IN VE N TORS (4 A law March 5. 1968 G. HLOCKWOOD ET AL 3,372,322

STEPPING MOTOR FEED FOR A GRINDER INCLUDING A HIGH SPEED SLEWING MOTOROriginal Filed Oct. 16, 1963 '7 Sheets-Sheet 3 REVERSING CIRCUIT lipSEQUENCING 8 DRIVING CIRCUIT PULSE GENERATOR 30 /sec 8| INCREMENTCOUNTER FIG. 3

GEORGE H. LOCK WOOD GLENN D. JOHNSON EDWARD G. ROB/LLARD HENRY E. HIRVIINVENTORS.

March 5, 1968 c. H LOCKWOOD ET AL 3,372,322

STEPPING MOTOR FEED FOR A GRINDER INCLUDING A HIGH SPEED SLEWING MOTOROriginal Filed Oct. 16. 1963 7 Sheets-Sheet 4 HIP-FLOP 93 osc/unrolzGEORGE H. LOCKWOOD GLENN D. JOHNSON EDWARD G. ROBILLARD HENRY E. H/RVIIN VEN TORS.

G. H. LOCKWOOD ET 3,372,322 STEPPING MOTOR FEED FOR A GRINDER INCLUDINGMach 5, 1968 A HIGH SPEED SLEWING MOTOR Original Filed Oct. 16. 1963 7Sheets-Sheet E HENRY E. HIRV/ INVENTORS.

March 5, 1968 G. H. LOCKWOOD ET AL STEPPING MOTOR FEED FOR A GRINDERINCLUDING A HIGH SPEED SLEWING MOTOR Origin-a1 Filed Oct. 16. 1965 '7Sheets-Sheet NM m K S M I. N CNBV E wmmw MJ H 1 RY MW R f WM GQEH B wt 5United States Patent C) 3,372,322 STEPPING MOTOR FEED FOR A GRINDERINCLUDING A HIGH SPEED SLEWlNG MOTGR George H. Lockwood, Worcester,Glenn D. Johnson, Sterling, Edward G. Robillard, Leicester, and Henry E.Hirvi, Paxton, Mass., assignors to The Heald Machine Company, Worcester,Mass., a corporation of Delaware Continuation of application Ser. No.316,756, Oct. 16, 1963. This application July 11, 1967, Ser. No. 652,625

. 3 Claims. (Cl. 318-39) ABSTRACT OF THE DISCLOSURE The presentinvention relates to a grinding machine, more particularly, to agrinding machine having a feedscrew for moving the wheel head to bringabout a machining operation, the feedscrew being operated by a steppingmotor which in turn receives pulses from a generator; a means isprovided for regulating the transmission of the pulses to the motor andrestricting the said transmission to the time when the spindle is at theend of a longitudinal stroke. In addition, means is provided fortransmitting selectively pulses of substantially different frequency.

This is a continuation of our copending application Ser. No. 316,756,filed Oct. 16, 1963, now abandoned.

This invention relates to a machine tool and, more particularly, to agrinding machine arranged to machine an internal surface of revolutionin a workpiece.

In the operation of grinding machines and other types of machine tools,it is common practice to feed the tool toward the workpiece surface atthe ends of a tool stroke when the tool is out of contact with thesurface. This type of feeding must be done in relatively smallincrements, While there are other situations when it is desirable tomove the tool toward the workpiece at a rapid rate or at an intermediaterate. Furthermore, it is desirable to be able to adjust the size of theincrements of feed which take place. In order to accomplish all of thesefunctions in a single feed mechanism, it is necessary to provide a verycomplicated mechanical construction. Such a mechanism gets out of ordereasily and requires constant attention to keep it in operatingcondition. In the past, such feed mechanisms have been limited tocertain geometric arrangements of the machine tool and lack offlexibility of design layout furnished when the feeding takes place bythe use of electrical means. Furthermore, finely adjustable feedmechanisms have been limited to use with small machine tools in whichthe elements to be moved are relatively light in weight. These and otherdifiiculties eX- perienced with the prior art have been obviated in anovel manner by the present invention.

It is, therefore, an outstanding object of the invention to provide amachine tool having a means for feeding the tool toward the work at aselected rate varying from very high speed to a very slow speed.

Another object of this invention is the provision of a grinding machinehaving a flexible feed mechanism capable of a wide range of speeds andwhich is not limited to a specific geometric layout of the machineelements.

A further object of the present invention is the provision of a grindingmachine having a feed mechanism which is relatively simple in operation,which is inexpensive to manufacture, and which is capable of a long lifeof useful service with a minimum of maintenance difiiculty.

It is another object of the instant invention to provide a grindingmachine having a feed means which is predominantly electrical incharacter and which is not subject to the geometric layout limitationsexperienced with a mechanical feed.

With these and other objects in view, as will be apparent to thoseskilled in the art, the invention resides in the combination of partsset forth in the specification and covered by the claims appendedhereto.

The character of the invention, however, may be best understood byreference to one of its structural forms as illustrated by theaccompanying drawings in which:

FIG. 1 is a perspective view of a machine tool em' bodying theprinciples of the present invention;

FIG. 2 is an enlarged view of a portion of the invention;

FIG. 3 is a schematic view of and FIGS. 4, 5, 6, and 7 are electricalschematics of circuits forming a part of the present invention.

Referring first to FIG. 1, which best shows the general features of theinvention, the machine tool, indicated by the reference numeral 10, isshown for the purposes of illustration as a vertical internal grindingmachine. The machine tool consists of a base 11 from which rises avertical mounting plate 12. Fastened to the forward surface of themounting plate is fastened a horizontal rail 13 whose vertical positionmay be adjusted on occasion by means of a hydraulic cylinder (notshown). The horizontal rail is provided with horizontal ways on whichare mounted a left saddle 14 which carries a wheelhead 15 and a rightsaddle 16 on which is mounted a wheelhead 17. Also mounted on themounting plate 12 is a lower saddle 18 carrying a wheelhead 19 whoseaxis is horizontal, the axis of the wheel heads 15 and 17 beingsubstantially vertical.

Mounted on the base 11 is a work table 21 mounted for rotation on avertical axis and driven by an electric motor (not shown). The worktable has a horizontal upper surface 22 adapted to support and hold aworkpiece 23 which, for the purposes of illustration, is shown as theinner race of a large, double, tapered-roller bearing. Along the back ofthe mounting plate 12 is located a control cabinet 24 from which extendcontrol wires, some of which pass through a hollow arm 25 which ispivotal about a vertical axis at the rear of the machine, which extendsforwardly and then downwardly, and which terminates in a pendant controlbox 26.

The wheelheads 15 and 17 are mounted on their saddles 14 and 16,respectively, in conjunction with a swivel means which permits the axisof the wheelhead spindle to be adjusted to a selected angle to thevertical, the axis, however, always remaining in a vertical planeparallel to the front surface of the mounting plate 12. For the purposesof illustration, the description of the controls will be confined to thewheelhead 15, but it will be understood that the wheelheads 17 and 19are similarly provided with means for reciprocating and feeding them.

The wheelhead 15 consists of a housing 27 in which is slidably mounted alarge spindle sleeve 28. The sleeve 28 carries a concentric spindle (notshown) at the end of which is mounted an abrasive wheel 29. On the upperpart of the left saddle 14 is mounted a meter 31 indicating the rate ofspindle rotation.

FIG. 2 shows the details of the control box 26 having at its upperportion a meter 32 which registers the speed of the rotation of the worktable 21 and under it is located a knob 33 for regulating this speed ofrotation. At one side of the meter is a coolant off-on switch 34, atable start button 35, and a table stop button 36. At the right part ofthe apparatus;

\ side of the meter 32 is a warning light 37 which indicates when thelevel of lubricant fluid in the tank is low. Beside it is anotherwarning light 38 which lights up when lubricant pressure is missing fromsome important part of the machine. At the same side of the meter is atable direction switch 39 as well as a table jog button 41. Extendingalong the right side of the control box 26 is an emergency bar 42 which,when struck, will shut down the machine in its entirety. The remainderof the surface of the box is occupied by control buttons arranged inthree groups: a left-hand group 43, which has to do with the wheelhead15, a central group 44, which has to do with the right-hand wheelhead17, and a right-hand group 45, which has to do with the lower wheelhead19. Since, as has been stated, the controls for the three wheelheads aresubstantially the same, the description will be limited to the left-handgroup 43, it being understood that the controls for the groups 44 and 45are almost exactly similar.

At the top of the left-hand group 43 is a feed dial 46 which shows theamount of feed of the wheel 29 toward the surface of the workpiece 23since the last time the dial has been reset. This feed dial works bothforwardly and backwardly to show the exact position of the wheelrelative to the workpiece. Immediately underlying the feed dial is amanual feed switch 47 capable of being turned either to a retractposition, a pick position, or a neutral position in between. Beside thislast switch is a feed dial reset switch 48, which is shown in a neutralposition but which is capable of being turned to a CCW or a CW position,these indicating either counter-clockwise or clockwise resetting of thefeed dial 46. Underlying the manual feed switch 47 is a saddle switch 49which is shown as positioned in an off position. It may be moved to theleft to a slow or a rapid position, or it may be moved to the right to aslow ora rapid position. To the right of the switch 49 is a feed switch51 which occupies either a left or a right position. Underlying thesaddle switch 49 is a feed at switch 52 which is capable of beingpositioned at any one of three positions, namely top, both, or bottom.To the right of the switch 52 is an auto feed switch 53 capable ofoccupying either an o or an on position. Underlying the feed at switch52 is a feed increment knob 54 which is calibrated in millimeters andwhich can occupy the pointer positions from to .014. To the right ofthis knob is a facing switch 55 capable of occupying either an off or anon position. Underlying the feed increment knob 54 is a slide switch 56having three positions, namely, down, auto, or up. To the right of theslide switch 56 is a vertical speed knob 57 which is calibrated to givea selection of desired vertical speeds in reciprocation of the wheel.Under the slide switch 56 is a wheelhead start switch 58 which is shownas occupying a neutral position but which may be turned to a CCW or a CWposition, indicating either counter-clockwise or clockwise rotation ofthe wheelhead and the wheel. To the right of the wheelhead start switchis a wheelhead stop button 59.

FIG. 3 shows, in a general way, the manner in which the reciprocationand feed of the wheel 29 takes place. The spindle 61 is shown as mountedschematically on the left saddle 14 which is driven horizontally acrossthe rail 13 by a main feed screw 62, there being a threaded engagementbetween the feed screw 62 and the saddle 14. In addition, the feed screw62 has mounted on it a nut 63 which is driven by a secondary feed screw64 which, in turn, is driven by a conventional three-phase inductionmotor 65. The main feed screw 62 is connected through a one-way clutch66 to a stepping motor 67. This stepping motor is of the type whoserotor rotates through small angular increments in response to thereceipt of electrical pulses. A pulse of a given polarity causes anincrement of rotation of the motor and it is not until a pulse of adifferent polarity is received that the motor proceeds in anotherangular increment of motion. Such a motor is the Slo- Syn motor which isthe trademark for the motor manufactured by the Superior ElectricCompany of Bristol, Conn., and the particular motor shown is their motortype X1000, which is capable of giving a torque of 1000 inch-ounces. Thedial 46 is connected to the shaft 68 of a dial stepping motor 69; thisstepping motor 69 is similar to the stepping motor 67 and is also of theSlo-Syn type manufactured by the Superior Electric Company of Bristol,Conn., and the particular motor used is their type $850, which producesa torque of 50 inch-ounces. Now, the motor is provided with electricalpulses originating in a pulse generator and increment counter circuit71,. which is connected to a sequencing and driving circuit 72, which,in turn, is connected to the motor 67 The circuit 72 may be used toconnect the motor 67 to a conventional 60 cycle alternating currentelectrical source. The circuit 72 may also be connected to the motor 65to drive it directly. The motor 69 is connected to the leads going tothe motor 67 in such a way that it receives the same pulses that thestepping motor 67 receives and rotates, therefore, in the sameincrements and direction to produce a change in the dial 46 indicativeof the amount of feed. Located adjacent the wheel 29 and operated bymagnetic dogs associated with it are two proximity switches 76 and 77,indicating the top and the bottom of the stroke. This stroke,incidentally, is produced by a hydraulic cylinder 78. The proximityswitch is connected to a reversing circuit 79 which has the function ofnot only energizing the switches but sending pulses through lines 81 and82 to a solenoid valve 83, which controls the flow of fluid to thecylinder 78 to reverse it and to assist in controlling its speed ofoperation.

FIG. 4 shows, in a somewhat schematic manner, the details of thereversing circuit 79. The circuit is a somewhat isolated electricalarrangement including a power line 84 connected to ground and a powerline 85 conuected to a 28 volts direct current source. The pickup headsof the proximity switches 76 and 77, of course, form a part of thecircuit, while the lines 81 and 82 control the valve 83. The lines 84and 85 are connected to opposite sides of the input of an oscillator 86which operates at 2700 cycles per second. The oscillator is, at course,connected to the heads of the proximity switches 76 and 77 and theoutputs of the switches are inserted into a dual amplifier 87 whichreceives its input power through lines 88 and 89 connected,respectively, to the power lines 85 and 84. The output of the amplifier87 appears on the lines 91 and 92. The line 91 is connected to theground 84 through a normally-open contactor 7X-1, while the line 92 isconnected to the ground through a normally-open contactor 8X-1.

The lines 91 and 92 are connected to the input of a flip-flop 93 whichreceives its power through lines 94 and 95 connected, respectively, tothe line 85 and the ground line 84. In addition, the flip-flop isconnected by a line 96 to a source of +8 volts D.C. electricity, whileit is also connected by a line 97 to a -160 volts D.C. source. Theoutput of the flip-flop is connected through the coil of a relay 4X tothe 28 volts line 85.

A line 98 is connected at one end to the ground line 84 and at the otherend connected to one end each of the coils of two relays 7X and 8X. Thecoil of the relay 7X is connected through a switch 99 to the line 85,while the coil of the relay 8X is connected through a switch 101 to theline 79, the switches 99 and 101 constituting parts of the slide switch56 (see FIG. 2). The line 85 is connected through a normally-opencontactor 4X-1 to one side of a 27-ohm resistor 102, the other sideofwhich is connected through one coil 103 of the 4-way servo reversingvalve 83 (see FIG. 3). Similarly, the line 85 is connected through anormally closed contactor 4X-2, through a 27-ohm resistor 104, andthrough the line 82 to one end of a coil 105 of the valve 83. The otherends of both coils 103 and 105 are connected directly to the ground line84. A ZSO-microfarad capacitor 106 is connected around the coil 103,while a similar 250- rnicrofarad capacitor 107 is connected around thecoil 105. A point between the normally-open contactor 4X-1 and theresistor 102 is connected by a line 108 to the input of a tarry timer109 and also to a line 111 leading to the feed circuitry, as will bedescribed hereinafter. The timer 109 is also connected by a line 112 toground. Similarly, a point between the normally-closed contactor 4X-2and the resistor 104 is connected by a line 113 to a tarry timer 114 andalso to a line 115 which goes with the line 111 to the feed circuitry.The timer 114 is con-. nected by a line 116 to the ground line 84. Thetimers 109 and 114 are joined by a line 117 and the central portion ofthe line 117 is connected to a speed control 118. The speed control isconnected by a line 119 to the high voltage line 85 and is connected bylines 121 and 122 to the line 112 leading to the ground line 84. Thespeed control 118 is also connected to ground through a coil 123 formingpart of a servo throttle valve 124 controlling the flow of fluid to thevalve 83 and, therefore, to the cylinder 78. In addition, the speedcontrol is also con nected through the coil of the relay 3X to theground line 84.

Referring now to FIG. 5, which shows the details of the pulse generatorand increment counter circuit 71, the circuitry is provided with a powerline 125 which is connected to a 28 volt D.C. source, and a line 126which is a common or ground line. In the circuit is located the feedincrement switch 54 which consists of three sections 127, 128, and 129.Section 127 has a contactor 131 capable of contacting any one of 8buttons numbered 0 through 7, the buttons 1, 3, 5, and 7 being connectedby a line 132 through the coil of a relay 9X to the ground line 126.Similarly, the section 128 is provided with a contactor 133 which isadapted to contact any one of 8 buttons, the buttons 2, 6, and 7 beingconnected by a line 134 through the coil of a relay X to the ground line126. The section 129 is provided with a contactor 135 which is adaptedto contact any one of 8 buttons, of which the buttons 4, 5, 6, and 7 areconnected by a line 136 through the coil of a relay 11X to the groundline 126. The contactors 131, 133, and 135 are mechanically connectedfor simultaneous movement over the buttons.

The manual feed switch 47 is made up of a switch 137 and a switch 138,one side of each of the switches 137 and 138 being connected to the highvoltage line 125. The other side of both of these switches is connectedto a line 139 which serves as a common connection for a number ofelements. First of all, the line 139 is connected to one side of thecoil of a relay X, the other side of this coil being connected to theground line 126 through a normally-open contactor 3X-1. Associated withthis part of the circuit is the auto feed switch 53 when in the onposition is closed and which is open when in the off position. Alsoassociated with this section of the apparatus is the feed at switch 52.This switch 52 is formed of two switches, 141 and 142. Now, the otherside of the coil of the relay 15X is connected through a normally-opencontactor 8X-1 and the switch 141 (forming part of the feed at switch52) and through the switch 53 to the ground line 126. Similarly, theother side of the coil of the relay 15X is connected through anormallyopen contactor 1X-1, through the switch 142, and through theswitch 53 to the ground line 126.

The common line 139 is also connected by a line 143 to the sequencingand driving circuits 72. It is also connected through a limit switch 144(mounted in the feed meter) to the line 125. The line 139 is alsoconnected to the ground line 126 through the following elements: thecoil of a relay 5X, a rectifier 145, a rectifier 146, and anormally-open contactor 15X1, these elements being mounted in series.The common point between the rectifiers 145 and 146 is connected to aline 147, while a common point between the rectifier 146 and thenormallyopen contactor 15X-1 is connected to a line 148. The line 147 isconnected to one post of a generator 149 capable of generatingelectrical pulses at a frequency in the neighborhood of 30 cycles persecond. The generator 149 is also connected by a line 151 to the highvoltage line 125. The line 147 is also connected through a normallyopencontactor 5X-1 to a line 152. The generator 149 is also connected to aline 153 leading to the sequencing and driving circuit 72.

Associated with this circuit are three flip-flops 154, 155, and 156. Theline 153 is connected to the flip-flop 154 which is also connected to a+6 volts D.C. source and a +160 volts D.C. source. The flip-flop 154 isalso connected through a rectifier 157 to the line 148 and by a line 158to the high voltage line 125. The flip-flop 154 is connected by a line159 to the flip-flop 155. The two flip-flops 154 and are also connectedthrough a normally-closed contactor 9X-1 and a normally-open contactor9X-2 mounted in series, there being a rectifier 161 connected betweenthe common point between these two contactors and the line 152.

Flip-flop 155 is connected by a line 162 to the ground line 126 and alsois connected to a source of +6 volts D.C. power and a -l60 volts D.C.source. This flip-flop is also connected through a rectifier 163 to theline 148 and connected by a line 164 to the high voltage line 125. Theflip-flops 155 and 156 are joined by a line 165 and they are also joinedby a normally-closed contactor 10X- 1 and a normally-open contactor10X-2 mounted in series with a rectifier 166 connected from the commonpoint between these two contactors and the line 152. The flipfiop 156 isconnected to the ground line 126 by a line 167 and is also connected toa source of +6 volts D.C. and a source of volts D.C. The flip-flop 156is connected through a rectifier 168 to the 1ine 148. It is alsoconnected through a line 169 to the high voltage line 125. One side ofthe flip-flop is connected to the other through a normally-closedcontactor 11X-1 and a normally-open contactor 11X-2 connected in series,the central point being connected by a rectifier 171 to the line 152.

FIG. 6 shows the layout of the sequencing and driving circuit 72. Thiscircuit is provided with a common or ground line 172 and a 28 volts D.C.line 173. Entering this circuit are the lines 111 and 115 originating inthe reversing circuit 79, the line 153 originating in the generator 149in the circuit 71, and the line 143 which originated in the incrementcounter of the circuit 71. Forming part of this circuit are threeflip-flops 174, 175, and 176 and a driver or amplifier 177. The line 173is connected through the coil of a relay 12X and a reset switch 178 tothe ground line 172. The line 111 is connected through the coil of therelay IX and through a IS-megohm resistor 179 to the ground line 172,there being a S-microfarad capacitor 181 connected across the resistor.Similarly, the line 115 is connected through the coil of the relay 2Xand through a l5-megohm resistor 182 to the ground line 172, there beinga S-megohm capacitor 183 connected across the resistor 182. The line 143is connected through a coil of a relay 3X to one side of a 15- megohmresistor 184 across which is connected a S-microfarad capacitor 185.Associated with this portion of the circuit are two switches 186 and 187forming further parts of the manual feed switch 47. Two sides of theseswitches are connected to the ground line 172. The other side of theswitch 186 is connected by a line 188 to the other side of the resistor184. The other side of the switch 187 is connected through a rectifier189 to the other side of the resistor 184. Furthermore, a common pointbetween the switch 187 and the rectifier 189 is connected through arectifier 191 and the coil of a relay 6X to the high voltage line 173. Acommon point between the rectifier 191 and the coil of the relay 6X isconnected to a buss line 192 which is connected through the coil of arelay 13X to the high voltage line 173. The line 172 is also connectedthrough the coil of a relay 14X to the high voltage line 173.Furthermore, the line 192 is connected through a normallyopen contactor6X1 and a normally-closed contactor 15X-1 to the ground line 172.

The line 153 is connected to the flip-flop 174 which,

in a manner similar to all of the flip-flops 174, 175, and 176, isconnected to a +6 volt D.C. source and a 160 volt D.C. source. One sideof the flip-flop 174 is connected by a line 192 to the high voltage line173, while the other side is connected by a line 193 to the ground line172. The flip-flop 174 is also connected to a .OOS-microfarad capacitor194 and through a 4.7-rnegohm resistor 195 to the ground line 172. Theflip-flop 174 is also connected through a .OOS-microfarad capacitor 196and a 4.7- megohm resistor 197 to the ground line 172. A common pointbetween the capacitor 194 and the resistor 195 'is connected to a commonpoint between the capacitor 196 and the resistor 197 by anormally-closed contactor 13X-1 and a normally-open contactor 13X-2 inseries. Similarly, the same common points are connected by anormally-open contactor 14X1 and a normally-closed contactor 14X-2 inseries. The common point between the two contactors 14X-1 and 14X-2 isconnected by a line 198 to the flip-flop 175 which is connected by aline 199 to the ground line 172 and by a line 201 to the high voltageline 173. A common point between the contactors 13X-1 and 13X-2 isconnected by a line 202 to the flipflop 176 which is connected by a line203 to the high voltage line 173 and is connected to the ground line 172by a line 204. The output of the flip-flop 176 is connected by a line205 to the input of the amplifier 177, while the output of the flip-flop175 is similarly connected to the amplifier by a line 206. A commonpoint 207 in the circuitry is connected to the flip-flop 174 by arectifier 208, to the flip-flop 176 by a rectifier 209, to the flip-flop175 by a rectifier 211, and to the ground line 172 through anormally-open contactor 12X-1. The amplifier 177 receives its power by aline 212 connecting it to the high voltage line 173 and by a line 213connecting it to the ground line 172. The output of the amplifier isconnected to the high voltage line 173 through the coil of a relay 1CRand to a coil of a relay 2CR. These coils form part of a circuit 216which is shown in detail in FIG. 7 and are connected to the amplifier bylines 217 and 218, respectively.

The circuit'216 shown in FIG. 7 is provided with main power lines 219and 221 connected to a llO-volt A.C. electrical source. In the circuitis shown the main stepping motor 67 with its operating coils 214 and215. Also included in the circuit is the dial stepping motor 69 havingoperating coils 222 and 223. The circuitry includes the saddle switch 49and a relay box 225. To begin with, the lines 217 and 218, originatingin the sequencing and driving circuit 72, are, as has been describedabove, connected to the power line 173 by the coils of the relays lCRand 2CR. The contactors associated with these relays (namely, thenormally-open contactor 1CR-1, the normally-closed contactor 1CR-2, thenormally-closed contactor 2CR-1, and the normally-open contactor 2CR-2)are associated in series with, respectively, the coils of relays lPR,3PR, 4PR, and 2PR, these relays being of the power type. The last-namedconnectors and their associated relays are connected to a source of1l0-volt A.C. electricity. Also associated with the relay 2CR arenormally open contactor 1CR-3, normally-open contactor 1CR-4,normally-closed contactor 1CR-5, and normally-closed contactor 1CR6.Similarly, associated with the relay ZCR, are normallyclosed contactor2C-R-3, normally-closed contactor 2CR 4, normally-open contactor 2CR-5,and normally-open contactor 2CR-6. These are connected to a source of-35 volt and +35 volt D.C. electricity and are connected to rectifiersand resistors in the manner shown. In accordance with the settings ofthe last-named series of contactors, the +35 or +35 volt D.C.electricity is imposed on lines 226 and 227 leading to the dial steppingmotor 69. The power relays are also provided with contactors 1PR1,2PR-1, 3PR1, and 4PR-1 which are connected to a source of volts DC and+10 volts DC. in the manner shown; they are also inter-connected withrectifiers and resistors. According to the settings of these contactors,

8 the +10 volts and +10 volts DC. electricity is impressed on lines 228and 229 leading to the stepping motor 67.

In the circuitry is included the feed dial reset switch 4-8 whichconsists of two switches 231 and 232, one side of each of which isconnected to the power line 221. The other side of the switch 231 isconnected by a line 233 through a normally-open contactor 1CR-8 to theside of the coil 222 of the dial stepping motor 69 that is not connectedto the power line 219. Similarly, the other side of the switch 232 isconnected by a line 234 through a normally-open contactor 1C\R9 to theouter end of the coil 223 of the stepping motor 69. The line 227 isconnected through a normally-closed contactor 1CR-7 to the outer end ofthe coil 222, while the line 226 is connected through thenormally-closed contactor 1CR-10 to the outer end of the coil 223. Aphasing network consisting of a resistor 235 and a capacitor 236connected in series is connected between the two lines 233 and 234. Thefeed switch 51 is also located in the circuitry and consists of a seriesof four switches 237, 238, 239, and 241. The line 228 is connected toone side of the switch 238 and one side of the switch 239. The otherline 229 is connected to one side of the switch 237 and one side of theswitch 241. The other side of the switch 237 is connected to a line 242,while the other side of the switches 241 and 239 are connected togetherand to a line 243. The saddle switch 49 consists of five sets of fourbuttons each, the sets being numbered 1, 2, 3, 4, and 5 and theindividual buttons in each set being lettered a, b, c, and d, therebeing, therefore, 20 buttons in all. A contactor 244 works across thebuttons in the 0 row and is connected back to the power line 221 througha normally-open contactor 2CR7. A similar contactor 245 is connectedthrough a normally-open contactor 1CR- 11 to similar networks associatedwith the other wheelheads of the machine, the contactor 245 workingalong the [2 row. The a row is engaged by a contactor 246 which isconnected by a line 247 directly to the outer end of the coil 214 of thestepping motor 67, the other end of which is connected to the groundedpower line 219. The d row of buttons is engaged by a contactor 248 whichis connected directly by a line 249 to the outer end of the coil 215 ofthe stepping motor 67, the other end of which is also connected to thepower line 219. Buttons 1a, 1b, 1c, and 1d are the row indicated asrapid left movement. The buttons 2a, 2b, 2c, and 2d are in a row whichis labeled slow left. The row 3a, 3b, 3c, and 3d (where the contactorsare shown as engaged) is the off position. The row of buttons 4a, 4b,4c, and 4d are the row known as slow right, while the row of buttons 5a,5b, 5c, and 5d are in the row known as rapid right. Buttons 1a, 3a, and5a are connected directly to the line 242. The buttons 1d, 3d, and 5dare connected directly to the line 243. The buttons 2a, 4a, and 4b areconnected to a line 251, while buttons 2d, 2c, and 4d are connected to aline 252. The lines 251 and 252 are joined by a phasing networkconsisting of a resistor 253 and a capacitor 254. In addition, thebutton 10 is connected to a line 255, while the button 5b is connectedto a line 256. The lines 255 and 256 are connected through the starterrelays 257 of the rapid traverse motor 65.

The operation of the invention may be readily understood in view of theabove description. The machine tool of the invention is shown as avertical grinding machine with a large diameter table and equipped withtwo vertical grinding slides and a horizontal grinding slide to performa variety of grinding operations. These operations include internal,external, tapering, shoulder, lip, face, and surface grinding. Theslides are reciprocated automatically or under manual control, the speedand direction being controlled from the swiveling pendant and thecontrol box 26. Both vertical saddles can be positioned horizontallyalong the mounting plate or cross-rail 12 and the horizontal slide canbe positioned vertically on the right-hand column of the machine. Thecross-rail 12 can be elevated to any height depending on the type ofwork to be done.

The most frequently used controls are located on the pendant in front ofthe machine. This pendant is sectioned according to its four functions;at the top is located the table control, coolant switch and thelubrication lights. The table controls, as has been pointed out, providefor starting, stopping, jogging, and for direction as well as a directreading speed meter and a speed control knob. The lower left section ofthe control box carries the left grinding compound controls. Theseinclude a directional wheel switch, a start switch, and a stop button.There are also controls for horizontal feed of the wheel against thework and for speed, direction, and automatic reciprocation of thevertical slide. At the top of this section is a direct reading feedmeter which displays the action of the cross feed under all conditionsexcept slow and rapid traverse. It also has a knob for the operator torecord the amount of compensation for wheel wear. The facing switch 55locks the grinding slide to the facing mechanism which can then be fedup and down by means of a hand wheel on the slide. The remaining twopendant sections are for the right vertical compound and the sidecompound and are identical to the left compound controls except that theside compound does not include the facing function. At the bottom alongthe side of the pendant is the emergency stop bar 42 which stops allmachine functions. The pendant swivels to any area around the machine.Less frequently used controls are placed on a panel on the back side ofthe machine. The grinding slide tarry or dwell is set for the requiredduration in the range from to 20 seconds. The tarry at the top and atthe bottom or left and right (for the side head). can be setindependently of one another. In addition, there are the hydraulic powerstart and stop buttons, an emergency stop button, a cross-railauto-unclamp switch, a stop reset button, lubrication lights, and alubrication injector button which should be pushed several times priorto operating the machine.

The grinding slide reciprocation reversal is accomplished by means ofthe manually positioned proximity switches 76 and 77. Precise locationof the bottom reversal point is achieved by screwing the proximity leafup and down from a nearest rack tooth interval. Loosening four swivelclamp bolts permits swiveling either slide at an angle of up to 45 oneither side of the vertical by means of a ratchet wrench provided withthe machine. This swiveling should be done with the slide at the bottomof its travel. At the lower edge of the grinding saddle is an opticalposition indicator which permits grinding of a series of parts to thesame diameter. When a grinding wheel is in a position to start a grind,or at any time that the grind must be interrupted and a compound movedout of position, if the compound location is noted before being moved,it can be returned to its original location by stopping at this recordedindicator reading. When the dresser compensation is made, the feed metercompensating knob must be compensated the same amount, since the dresseris mounted on the feeding slide. At the top of the grinding slide is awheelhead motor load meter. The extension of the wheelhead should bekept as small as possible, consistent with the length of grind beingmade. This extension is changed as follows: secure the head againstfalling with a crane hook, loosen two screws on each end of the housingand then loosen four clamp screws in the housing end rings. Be carefulto clean the body of the wheelhead carefully before sliding it in orout. There is a tapped hole in the wheel end of the grinding spindlewhich may be used for extending or shortening the side head overhang,rather than using the eye bolt on the motor end.

To grind the top of the table or the workpiece clamps, incline theleft-hand wheelhead to 15 counter-clockwise. Dress olfthe wheel parallelto the table top with a diamond in a holder on the table. Reciprocatethe head using the slow traverse speed and switching from left to righttraverse with the pendant switch. Feed the head down- 10 ward by meansof the facing mechanism. Note that, unless the cross-rail is parallel tothe plane of the table thrust bearing, a concave or convex table topwill be the result.

When the cross-rail is leveled, a note should be made of the location ofeach of the saddles on the cross-rail. The right-hand saddle should bein its extreme right-hand position and the left-hand saddle should be insuch a position as to bring the grinding wheel with the head swiveled 15counter-clockwise. Taking these steps before leveling the rail willassure the best conditions for grinding the table top flat. When raisingor lowering the cross-rail, the best precision will then be obtained byputting the saddles in these locations. Also, if the cross-raildirection is up when the desired location is reached, the screws andgears will be loaded in the same manner as when the rail was leveled. Tolevel the rail, switch from auto to unclamp on the cross-rail switch.The cross-rail is raised and lowered by an electric motor on top of thecolumn. Speed is controlled by a hand throttle. The rail is clamped inposition by a double toggle-actuated pair of clamp arms actuated toclamp the rail. On the left-hand end of the cross-rail there are twopressure-reducing valves which control the pressure to thecounter-balance cylinders which assist the leveling screws,

In the preferred embodiment, a 15 horse power motor drives the tablewith 5 V-belts connecting the motor to a large pulley underneath thetable. The belt tension is maintained by a hydraulic cylinder whichslides the entire drive unit on the floor. Pressure is set by apressure-reducing valve in the service cabinet and the belts can beslackened by means of a lever-operated valve beside the pressurereducer. The machine feed and reversal system consists of anelectro-hydraulic control system for slide reciprocation and anelectro-mechanical system for saddle feed and traverse motion along afeed and traverse axis. The grinding slide reversal is a systemconsisting of the two proximity pick-up units or switches 76 and 77 thatwork into the transistorized amplifier 87. The amplifiers control thestate of the flip-flop system 93 which drives a mercury-wetted relay 4X.The contacts of the relay 4X energize the, servo-type directionalcontrol valve 83 which controls the reversal point of the grindingslide. The speed of the grinding slide is controlled by varying thevoltage on the coil 123 of the pressure-compensated servo throttle 124.Two independent dwells (which are adjustable from .1 to 20.0 seconds)are available at each end of the grinding slide by means of twotransistorized timing units 109 and 114. The dwell is obtained byclosing the servo valve 83 and de-energizing a mercury-wetted relay 3Xthat operates a stop valve.

The 10-volt 2700 cycles per second oscillator 86 is used to excite thepick-up units or switches 76 and 77. This oscillator consists of an R-Ctype two transistor oscillator which is transformer coupled into thepower amplifier circuit 87. The proximity switches 76 and 77 consist ofa primary and secondary coil in each unit. By means of laminated dogs onthe grinding slide, a voltage above quiescent is induced in thesecondary coil. This secondary voltage is fed into the dual amplifierunit 87. This unit consists of two 'pulse amplifiers and a bias circuit.The bias circuit operates from the 2700 cycle oscillator voltage whichis rectified and filtered to an output of +7 volts DC. By means of apotentiometer, the bias voltage for each input amplifier is used tocancel out the quiescent signal from the proximity pick-up units with nodog over the pickup. When a dog is positioned over a pickup, thesecondary voltage from the pickup will exceed the bias voltage andnegative pulses will appear at the output of the correspondingamplifier. The outputs of each amplifier are coupled to both sides ofthe flip-flop 93. The flip-flop will remain in either of two states ofconduction, depending upon which input signal was received last. Theoutput of the flip-flop operates the mercury-wetted relay 4X. This relayis either energized or de-energized depending upon the state of theflip-flop. The contacts of the 1 1 output relay 4X are used to controlthe servo valve 83 which controls the direction of the slide. Thesecontacts are also used to energize other relays through an R-C networkto provide signals to the feed system.

To cause an independent adjustable dwell in either or both ends of thegrinding stroke, the adjustable timing units 109 and 114 are used oneach of the two reversal points. These timers are adjustable in a rangeof .1 to 20.0 seconds. The outputs are connected together and work intoa voltage control unit 118. Whenever either of the two tarry timers istiming, the output of the voltage control unit is volt, whichde-energizes the servo throttle 124 stopping the slide. The voltagecontrol unit also de-energizes the mercury-wetted relay that operatesthe stop valve. The stop valve will hold the slide locked in the stopposition. When the timer times out the mercurywetted relay becomesenergized by the voltage control unit releasing the stop valve and thevoltage through the servo throttle returns to the set voltage. This willallow the slide to move to the other reversal point which will againcause the slide to stop for a pre-set time, depending upon the settingof the timer. The speed of the slide is controlled by the setting of thepotentiometer in the speed control unit 118. This unit contains a powertransistor connected 'as an emitter follower with the servo throttlecoil for the load. The voltage on the servo throttle is variable from Oto 27 volts D.C. with the potentiometer in this unit.

The feed mechanism for the machine is an electromechanical system. Thesystem consists of a grinding saddle which is moved along a feed andtraverse axis by means of the ball screw 62. The travel along this feedand traverse axis is limited by limit and interference switches. Theball screw is rotated in either direction in any of the following threemodes:

(1) Rapid traverse by means of the motor 65 which, in the preferredembodiment, is a A; horsepower, 1725 rpm, 225 volt, 3-phase, 60 cyclessaddle traverse motor. The traverse rate is 36 inches per minute withthis motor.

(2) Slow traverse by means of the 1,000 ounce-inch synchronous steppingmotor 67 which, in the preferred embodiment, runs on 110 volts singlephase 60 cycles per second. This motor is located on the cross-rail 13in the case of the vertical wheelheads and on the right-hand column forthe horizontal wheelhead. In the preferred embodiment, the slow traverserate is /1 of an inch per minute.

(3) Incremental feeding by means of the same 1,000 ounce-inch steppingmotor 67 operating in a 200 step per revolution mode. Rotation of themotor is accomplished by supplying a volt D.C. supply to each motorwinding and switching the motor winding polarity in an establishedsequence. The motor shaft moves /2()() of a revolution or 1.8 for eachswitching of polarity. The number of steps per feed cycle is selected bymeans of the 8-position switch 54- (which is calibrated in millimeters).This means that up to seven incremental steps can be selected per cycle.The feed meter 46 located on the pendant (one for each grinding saddle)shows the amount of feed in the incremental feeding mode. A microswitchlocated in this feed meter will stop the automatic feed when the feedmeter reaches 0. This switch can be overridden by the manualpick-retract switch 47 located on the control box. The mode of saddlemovement is selected by means of the 5-position spring-return-to-centersaddle switch 49 located on the control box.

Reference should be made to FIGS. 5, 6, and 7 in connection with thedescription of the incremental feeding mode apparatus describedhereinafter. The circuit can be broken down into a counting section, asequencing selection, a pulse generator, and a stepping motor drivingunit. The counting section of the system consists of the three 1flip-flops 154, 155, and 156 connected as a binary counter.

12 have been received. The desired count is selected by use of the feedincrement switch 54 on the control box. This feed increment switchcontrols mercury-wetted relays 9X, 10X, and 11X which are necessary inorder to isolate the feed system from the machine wiring, otherwise Itransient voltages would cause erratic operation of this system.

The sequencing section shown in FIG. 6 consists of the three flip-flops174, 175, and 176, a relay drive or amplifier 177, and mercury-wettedrelays 6X, 13X, and 14X. The input flip-flop 174 is triggered by thegenerator pulses. The two outputs from this flip-flop are fed into theflip-flops 175 and 176 through the relay contactors 13X1, 13X2, and14X1, and 14X-2. These relays along with the relay 6X are used toreverse the sequencing which reverses thedirection of the stepping motor67. This is accomplished by inter-changing the inputs of flipflops 175and 176. Differentiating networks consisting of the resistor and thecapacitor 194, on the one hand, and the resistor 197 and the capacitor196, on the other hand, are required to prevent the flip-flops 175 and176 from being triggered when their binary leads are switched. Theoutputs of the flip-flops 175 and 176 are connected to twotransistorized driver amplifiers 177 which control two 28-volt D.C.relays 1CR and 2CR in the stepping motor driving unit (FIG. 7).

The generator 149 consists of an R-C network used to determine the pulseor step-rate of the system. This R-C network works into a unijunctiontransistor which produces pulses when the command line is grounded. Thepulse rate is adjusted by means of a trim potentiometer located on thegenerator mount.

As is evident in FIG. 7, the driving unit includes 228 Volt DC. controlrelays 1CR and 2CR. Contacts of these relays are used to control thefour power relays lPR, ZPR, 3PR, and 4PR. The power relay contacts areused to switch the polarity of the IO-volt D.C. supply to the 1,000ounce-inch stepping motor 67. This is done in the proper sequence whichis established by the flip-flops 174, 175, and 176.

Another set of contacts from the control relays lCR and 2CR are used toswitch the polarity of the 35-volt D.C. supply to the dial steppingmotor 69. This motor is located in the feed meter 46 which, of course,is mounted on the control box. A resistor diode arrangement is used toprotect the contacts of the l00-volt DC. power relays. The contacts ofthe -28 volt D.C. relay, which switches for the benefit of the dialstepping motor 69, are also protected in the same manner.

The feed cycle operates as follows: the system is turned on and the rearpush button 128 located in the rear station is pressed. A contact blockfrom this button ener gizes the relay 12X which sets the threesequencing flipfiops 154, 155, and 156 to their high state insuringcorrect feed direction. A feed increment is set on the feed incrementswitch 54 which energizes the relays 9X, 10X, and 11X in a binary codedrelationship. This determines the number of pulses to be accepted by thecounter and, in turn, the steps which the stepping motors will makeduring the feed cycle. The contacts of these relays are connected to thecommand line through an OR network of diodes. A cycle start signal issupplied to the system through either the relay 1X (slide up reversalpoint on the vertical wheelheads), 2X (slide down reversal point), or 3X(pick-retract). One of these relays will momentarily close by means ofan R-C network in series with the relay coil. The momentary closure ofone of these contacts will cause the relay 15X to pulse in. This willset the counter flip-flops to their low state in preparation to count.The relay 15X also actuates the relay 5X and energizes the command line.The relay 5X will rock up through the counter flip-flops 154, 155, and156 and keep the command line energized. This starts the pulse generator149 which continues to pulse until the set count is reached. When thisset count occurs, all

13 of the flip-flop outputs which are connected to the command line willbe above ground. This will stop the generator 149 and allow the relay Xto de-energize completing the counting cycle.

While the generator 149 is operating, its pulses are also being fed tothe sequencing flip-flop 174 (FIG. 6). This flip-flop is driving theother two sequence flip-flops 175 and 176 in accordance with theposition of the direction setting relays 6X, 13X, and 14X. The outputsof the last two flip-flops are amplified in the driver or amplifier 177and used to actuate the 28-volt D.C. relays R and 2CR in the drivingunit.

It is obvious that minor changes may be made in the form andconstruction of the invention without departing from the material spiritthereof. It is not, however, desired to confine the invention to theexact form herein shown and described, but it is desired to include allsuch as properly come within the scope claimed.

The invention having been thus described, what is claimed as new anddesired to secure by Letters Patent is:

1. A grinding machine for machining a surface of revolution in aworkpiece, comprising (a) a workpiece table having a work surface,

(b) a wheelhead having a spindle extending toward the table,

(c) a feed screw for moving the wheelhead relative to the table to bringabout the said machining,

(d) a stepping motor operatively connected to the feed screw androtative in a small increment in response to the receipt of anelectrical pulse,

(e) a generator of electrical pulses,

(f) means selectively adjustable to regulate the trans mission ofelectrical pulses from the generator to the stepping motor, and

(g) means to reciprocate the wheelhead spindle longitudinally in apredetermined stroke, the said selectively-adjustable means operating totransmit pulses from the generator to the stepping motor only at the endof a stroke.

2. A grinding machine as recited in claim 1, wherein means is providedfor selectively connecting the stepping motor to a conventional sourceof sixty-cycle per second alternating current electricity, the pulsesfrom the said soufce being impressed on the stepping motor continuous y.

3. A grinding machine for machining an internal surface of revolution ina workpiece, comprising (a) a workpiece table having a work surface,

(b) a wheelhead having a spindle overlying the table,

(0) a feed screw for moving the wheelhead relative to the table to bringabout the said machining,

(d) a stepping motor operatively connected to the feed screw androtative in a small increment in response to the receipt of anelectrical pulse,

(e) a generator of electrical pulses,

(f) means selectively adjustable to regulate the transmission ofelectrical pulses from the generator to the stepping motor, the saidmeans comprising a plurality of flip-flop circuits arranged to admit tothe stepping motor a selected number of the total pulses emitted fromthe generator, the said means also including an increment counterconnected on its input side to receive all the pulses from the generatorand to emit from its output side a predetermined number of all thepulses, the output of the counter being connected through an amplifierand a sequencing circuit to the stepping motor, the operation of thesequencing circuit serving to determine the direction of rotation of thestepping motor,

(g) a conventional electrical motor also connected to the feed screw forhigh speed operation thereof, and

(h) means for alternately presenting to the stepping motor pulses fromthe generator or pulses from a -cyc1e per second alternating currentsource.

References Cited UNITED STATES PATENTS 2,674,706 4/1954 Knosp et a1.318-39 X 2,687,759 1/ 1959 Comstock.

3,015,806 1/1962 Wang et a1.

3,089,988 5/1963 Stillings.

3,191,205 6/ 1965 Gilbert.

3,231,801 1/1966 Lang 31049X 3,246,218 4/ 1966 Centner et a1. 318-8 ORISL. RADER, Primary Examiner. T. E. LYNCH, Assistant Examiner.

